Ketoconazole in pityriasis versicolor with monitoring its serum level using a simple bioassay technique

ABSTRACT

A simple agar-well diffusion bioassay method for measurement of ketoconazole was evaluated in which a medium containing 0.7% trypticase peptone and a strain of Candida pseudotropicalis as assay organism were used. A linear relationship between zone diameters and Log 10 concentrations of the drug over the pharmacologically relevant ranges of 0.5-20 mug/ml was obtained [F=1324.038; p <0.001]. The variability among measurements was found to be 0.3421 denoting that the technique was precise and hence was used to monitor serum level of patients of this study. Twenty two patients with pityriasis versicolor therapeutically received a ten-day course of ketoconazole to investigate the efficacy of this short course of the drug. Patients were assessed both clinically [for scaling and pigmentation] and laboratory [KOH scraping] before starting ketoconazole therapy, at the end of the course [day 10] and on day [30]. Serum ketoconazole levels of patients ranged from 0-6.9 mug/ml on the second day of therapy and 0.9-7.1 mug/ml on day [10]. Before starting therapy, all patients showed positive KOH preparation, 21 [95.5%] showed scaly lesion and 12 patients [45.5%] had pigmented lesion. On day [30] only one patient had scaly lesion while two patients still had pigmented lesion and KOH positive smear. The improvement seen in both clinical and laboratory parameters in the follow-up period was highly significant [P <0.001] when compared to pretreatment figures. The 10-day course of ketoconazole in the treatment of pityriasis versicolor was recommended